A Study of Atezolizumab Plus Cobimetinib and Vemurafenib Versus Placebo Plus Cobimetinib and Vemurafenib in Previously Untreated BRAFv600 Mutation-Positive Patients With Metastatic or Unresectable Locally Advanced Melanoma

Inclusion Criteria: * Females of child bearing potential and males with female partners must and use of contraceptive methods with a failure rate of less than or equal to (\</=)1% per year is required during treatment and for 6 months post treatment. Males should not expose pregnant partners to sperm and refrain from donating sperm for 6 months post treatment. Women must refrain from donating eggs during this same period * Histologically confirmed Stage IV (metastatic) or unresectable Stage IIIc (locally advanced) melanoma * Naive to prior systemic anti-cancer therapy for melanoma (example: chemotherapy, hormonal therapy, targeted therapy, immunotherapy, or other biologic therapies) except adjuvant treatment with interferon (IFN), interleukin (IL)-2, or vaccine therapies or herbal therapies * Documentation of BRAFv600 mutation-positive status in melanoma tumor tissue (archival or newly obtained) through use of a clinical mutation test approved by the local health authority * Eastern Cooperative Oncology Group Performance (ECOG) Status of 0 or 1 * Measurable disease according to RECIST v1.1 (must be outside central nervous system (CNS)) * Life expectancy \>/=18 weeks * For participants not receiving therapeutic anticoagulation: International normalized ratio (INR) or activated partial thromboplastin time (aPTT) less than or equal to (\</=) 1.5\*upper limit of normal (ULN) within 28 days prior to initiation of study treatment * For participants receiving therapeutic anticoagul…